The crystalline transformation of vaterite in the presence of copper(II) [Cu(II)] has been investigated in ultrapure water and at room temperature using several techniques; scanning electron microscopy (SEM), infrared (IR) and micro-Raman spectroscopy. Our findings show that a slowing down of this transformation occurs and is intimately related to the generation of CuCO 3 layers on CaCO 3 surfaces. This phenomenon is also accompanied by a decrease of vaterite solubility. All these observations have led us to suggest that these Cu(II) coatings prevent the dissolution of the metastable calcium carbonate, vaterite. To prove this suggestion, experiments on solubilities of Cu 2+ -vaterite solids were performed and interpreted in terms of thermodynamic equilibrium and stoichiometric saturation concepts. Thermodynamic and spectroscopic data demonstrate that the apparent stabilization of vaterite in the presence of Cu(II) is strongly dependent on the existence of water molecules in the lattice of the solid solution Cu x Ca 1-x CO 3 as (H 2 O) y Cu x Ca 1-x CO 3 . The chemical composition of this complex has been determined by X-ray photoelectron spectroscopy and thermogravimetry. Thus, the free energy of formation of such hydrated Cu(II) complexes has been found to be slightly lower than that for calcite. However, for high Cu(II) concentrations, metallic multilayers cannot grow indefinitely, and malachite [Cu 2 (OH) 2 (CO 3 )] appears as a new phase. SEM and micro-Raman techniques have allowed successfully monitoring these morphological phenomena/transformation.